Apache complains about issuer of certificate

You get something like:

Certificate Verification: Error (20): unable to get local issuer certificate

You probably missed to set the OPENSSL_ALLOW_PROXY_CERTS variable on the Apache environment

Error 14: Signature error

You have to double check that the vomsdir_path and ca_path configuration options (that default to /etc/grid-security/vomsdir and /etc/grid-security/certificates respectively) point to the correct path. Also ensure that the .lsc files have the right contents and that the CLRs are up to date.